The correct DW Frost priority list

What is the correct priority list for Frost DW DK's since 5.1 for single target and AoE situations, and at what # of target's is it worth while to start AoE'ing? Also, is Relix of Xuen BiS outside of Heroics?

The difference between single-target and AoE priority for DW Frost? If you have more than 3 or 4 targets (check the damage for your own char) don't bother using SR as HB will do more damage, and that's about it. All your Frost and Death Runes go to Howling Blast; your Unholy Runes go to D&D and keeping up Blood Plague, and unfortunately sometimes Obliterate (Plague Leech really helps avoiding using it ), and your Runic Power for Frost Strike, obviously. See the EJ link above for the priority.

The difference between single-target and AoE priority for DW Frost? If you have more than 3 or 4 targets (check the damage for your own char) don't bother using SR as HB will do more damage, and that's about it. All your Frost and Death Runes go to Howling Blast; your Unholy Runes go to D&D and keeping up Blood Plague, and unfortunately sometimes Obliterate (Plague Leech really helps avoiding using it ), and your Runic Power for Frost Strike, obviously. See the EJ link above for the priority.

The problem with using OB for Unholy runes is that you have to look at the damage of a single OB versus that of HB + DnD. The latter will pretty much always be more, which means that you want to limit OB usage to when DnD is on cooldown.
So you're partially right; you do have to use OB at times, but you want to prioritize DnD as your Unholy rune spender.

I'm also really curious to know the "right" rotation as it's very difficult to find concordant information. Main EJ thread is clearly outdated and nobody seems to agree when we talk about the best way to use Unholy runes.
If we rely on the last simcraft profile (510-8) we notice OB takes priority over D&D to use Unholy runes, and D&D is really low in priority list.
My question is to know if we can consider the following priority list as the right rotation to maximize dps ?

In the case of duel wield, even before stacking mastery, 2 howling blasts hit harder than an obliterate, and as such howling blast takes a far more prominent spot in our priority. Unfortunately, while both frost and death runes can be used for said howling blast, unholy runes cannot, often leaving us with 2 ugly green runes to get rid of before we can go back to spamming HB and FS.
There are three ways to get rid of unholy runes, let's see which is the best.
Death and decay: 48.2k dmg
Plague strike: 23.2k dmg + 100k (full duration disease, 10k per 3 seconds)
Obliterate: 78.1k dmg +45% chance for free HB = 113.2k dmg
HB: 78.0k dmg

Obviously your best bet is double HBs whenever possible, but let's say you have 1 unholy and 1 frost/death, what should you do?
In order from best to worst:
Using plague strike and HB gives 201.2k dmg IF diseases are about to fall off
Using plague leech, plague strike and 2 howling blasts gives 179.2k dmg
Using DnD and HB gives 126.2k dmg
Using obliterate gives 113.2k dmg
Using plague strike and HB gives 101.2k dmg
Ignoring the unholy rune and just spending the frost/death on HB gives 78k dmg

While it's true you can use plague strike and howling blast at half disease duration and count the 50% refresh as 50k dmg, it prolongs the ability to fully refresh diseases via the top option for 15 seconds, and is therefore not a damage gain. If blood plague is not just about to fall off, count it as if it isn't refreshing at all.

So, if diseases are about to fall off, plauge leech is off cd, or dnd is off cd, use the above options to remove unholy runes, otherwise just use obliterate if you have to.

Note: Due to DW's current state of being close to GCD locked most of the time, we need to reexamine the way to deal with unholy runes. While the above-mentioned list is accurate in terms of numbers, obliterate is more complicated than it seems. Obliterate has two possibilities, it either does 78.1k in one GCD, or 156.1k dmg in 2 GCDs. While we can average this out easily, as done above, the GCD cost has to be considered. Using DnD/HB does slightly more than obliterate on average, but costs 2 GCDs. Using obliterate over DnD is a gain if you are GCD capped. Depending on luck, you'll either gain free damage with the rime proc, or gain a GCD which will avoid overflowing resources which will be a damage gain. If you are not GCD capped, DnD/HB wins out.

And yes, the simcraft profile is constantly updated and is most likely your best bet at a good rotation.

Thanks for that clarification. It was really bugging me that logically, DnD + HB would do more damage, but I couldn't get it to sim that way. But I wasn't taking into account the GCDs while GCD capped.

I have a question regarding DW burst: What would be the best setup for going into PoF? Would you try to go with no runes, high RP and just frost strike spam, then ERW and normal rotation? I can't seem to get good burst.